Our literature search of infectious endophthalmitis studies in a Korean population included Korean Med (http://www.koreamed.org/), Pubmed (http://www.ncbi.nlm.nih.gov/), and the search engine of The Korean Ophthalmological Society (http://www.ophthalmology.org/) with term “infectious endophthalmitis”. This search revealed 11 articles, excepting case reports [7-10,15-20]. All papers were single-center studies and had limited numbers of patients or needed a long study period to recruit enough patients for analysis. Among the studies, the largest had 59 total cases and 37 culture-positive cases over the course of about 10 years. The smallest patient population had 18 total cases and 8 culture-positive cases over about 5 years [8,16]. In this context, the present study with its large study population of 174 total cases and 103 culture-positive cases has an advantage in revealing the clinical characteristics of Korean infectious endophthalmitis.
The annual incidence of postoperative infectious endophthalmitis was 0.037% in Busan and Gyeongsangnam-do. In the Swedish study, 0.029-0.048% of cataract operations developed postoperative endophthalmitis [6,21]. Recently, the incidence rate of infectious endophthalmitis in Canada was 0.14% of cataract operations . A study in Singapore within the last 20 years revealed a rate of 0.076% . The incident rate of South Korea was similar with the previous reports. It is worth to comment the stepwise increase of postoperative endophthalmitis rate during the period (2007 ~ 2009).
The seasonal variations of postoperative endophthalmitis were investigated. Most of previous studies showed no significant association between infectious endophthalmitis and season. However, seasonal differences in development of infectious endophthalmitis were observed in our study. Spring appears the season that develop infectious endophthalmitis most commonly. To clarify the seasonal variation of infectious endophthalmitis, the authors analyzed the seasonal incidence rate of postoperative infectious endophthalmitis over 4 years. Even though after adjusting for the number of cataract procedures performed in each season, the incident rate of spring is significantly higher than the others. On the other hand, a study performed in Australia showed that endophthalmitis occurred more often after operations performed in winter and autumn than after those performed in spring and summer . But, the temperature of winter in Austrailia is similar to that of spring in South Korea. Rubio reported that conjunctival swab sample culture results had showed the frequency of bacteria had increased in April, May, and June, when the daily average temperature rises from 12°C to 22°C, this range is also similar to the temperature distribution of spring in South Korea . In this regards, season or temperature could be associated with incidence of postoperative endophthalmitis.
The relationship between patient sex and infectious endophthalmitis is not clear throughout the previous studies [2,6,22,24]. Our study showed a similar distribution between sexes.
Right eyes had higher incidence of infectious endophthalmitis in our study. Wong and Chee’s Singapore data showed no significant difference .
Age over 85 years is a known risk factor for postoperative infectious endophthalmitis [6,21,22]. In our study, 1% (2/197) of infectious endophthalmitis patients was over 85 years. Most patients were between their 7th and 8th decades (59.4%).
Medical history of the patients was most frequently hypertension (40.4%) and diabetes (23.4%). These findings are generally in accordance with previous studies that found hypertension in 39.8% and diabetes in 13.8% [2,7,9]. Interestingly, 35.6% of the patients did not have any systemic problems when they developed infectious endophthalmitis. Lee and Park also reported that 54.2% of patients had no medical history .
Cataract surgery was the most common cause of infectious endophthalmitis, among which 95.9% of the operations were uneventful phacoemulsifications without anterior vitrectomy. Recent studies showed similar data [6,22].
In 84 of 152 cases (55.3%), signs of endophthalmitis occurred within 3 days after the inciting events, and 130 of 152 cases (85.5%) had signs of endophthalmitis within 14 days after the inciting events. This range was also in accordance with a previous study . In 128 of 165 cases (77.6%), surgical interventions including pars plana vitrectomy, intravitreal antibiotics injection, or AC irrigation were performed within 3 days of endophthalmitis symptom onset.
The final visual outcome in this study was worse than previous studies [2,23,26]. Only 54 of 162 cases (33.3%) had final visual outcome over 20/100. EVS and Netherland studies showed that 74% and 68.8% of patients, respectively, achieved 20/100 or better vision. This difference could be explained by the included endophthalmitis categories and the microbiologic spectrum causing infectious endophthalmitis in our study. Traumatic and endogenous endophthalmitis groups were included in our study. Enterococcus faecalis was the most common causal bacteria in this study . Recently, the visual outcome of Sweden’s study, in which the most common microorganism was Enterococcus species, was worse than EVS and Netherland, even though all of these studies included post-cataract operation endophthalmitis. In 40 of 135 cases (29.6%), the visual outcome was 20/40 or better . Details about the factors related to the visual outcome are beyond this paper’s scope.
The rate of vitrectomy was 143 of 197 cases (72.6%), and the rate of only intravitreal antibiotic injection was 34 of 197 cases (17.3%). And the rate of vitrectomy as a primary treatment for infectious endophthalmitis was 65.5%. Even though the suggestion of the EVS study on postoperative endophthalmitis treatment, the surgeons who took part in this study preferred vitrectomy as the primary treatment rather than intravitreal antibiotic injection. The rate of vitrectomy as an early intervention in Netherland study was 25 of 250 cases (10%). However, the rate of vitrectomy in a recent Korean endophthalmitis study was 76.3%, which was similar to our current findings .
Culture positivity in our study was 103 of 174 cases (59.2%), which corresponded with the rates (54.4-69.3%) of the previous studies [23,26-29]. The higher positive culture rate in vitreous samples harvested during pars plana vitrectomy than in those harvested during intravitreal injection was quite interesting. This difference could be another advantage of vitrectomy as treatment for infectious endophthalmitis.
Infectious endophthalmitis could have different presentation, causative agents and therapeutic approaches depending on their different etiologies such as postoperative, traumatic, and endogenous endophthalmitis. Except the incidence of postoperative endophthalmitis, all kinds of infectious endophthalmitis were included and analyzed in this study. In this regards, the data in this study should be carefully interpreted and compared with the others results.